Pumps are used for many applications requiring the pumping of fluid and are often driven by an electric motor which operates at a single speed and has one coil or winding. Many motors have a second coil or winding which generates much higher power and is used as a starter winding to overcome the initial inertia of the pump and motor. Such a starter winding is usually activated for a period of less than a second after the motor is switched on before the main winding is engaged and the starter winding is disengaged.
Motors are typically designed to be able to deliver the maximum power needed for the particular application. Where motors are used for pumping fluids, this maximum power will be required to start the fluid flowing, which may take a few minutes, or when additional volume of fluid is suddenly required to be pumped, for instance. The design of motors to use enough power to handle the maximum load conditions results in an inherent energy inefficiency. This inefficiency results because more power is delivered to the motor than is needed at low load conditions, such as after a continuous flow has been established in a pumping system.
Some whirlpool spas utilize a two-speed motor which has, in addition to the starter winding, two additional windings enabling it to operate at a low speed and a high speed. The low speed is used for pumping water through a filtering system and the high speed is used for pumping water into the jets. A manual switch on the side of the motor enables it to be switched into the high speed mode for pumping through the jets when people desire to use the spa.